Re: join selectivity - Mailing list pgsql-hackers

From Tom Lane
Subject Re: join selectivity
Date
Msg-id 28399.1103814783@sss.pgh.pa.us
Whole thread Raw
In response to Re: join selectivity  ("Mark Cave-Ayland" <m.cave-ayland@webbased.co.uk>)
Responses Re: join selectivity
List pgsql-hackers
strk@refractions.net writes:
> On Thu, Dec 23, 2004 at 10:01:33AM -0500, Tom Lane wrote:
>> Right.  This amounts to assuming that the join conditions and the
>> restriction conditions are independent, which of course is bogus,
>> but we really don't have enough information to do better.

> Doesn't JOINSEL have access to RESTRICTSEL output for REL1 and REL2 ?

You could probably compare the fields of the RelOptInfo structures,
but what are you going to do with it?  AFAICS you *should not* make
the join selectivity depend on that.
        regards, tom lane


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